Finish testing method and apparatus



June 5, 1934. R. BURNS 1,961,333

FINISH TESTING METHOD AND APPARATUS Filed Oct. 23, 1929 2 Sheets-Sheet lF/G./ 2a

26 "11 1. v4 n 5 I 5 20 f It /6 I H /0 22 '1 i 27\ I 1 w m In H II finwmvrop R Bup/vs A77 PNEY JuneS, 1934. R BURNS 1,961,333

FINISH TESTING METHOD AND APPARATUS Filed Oct. 23, 1929 2 Sheets-Sheet 2/Nl EN 70/? R BURNS A O/PNE) Patented June 5, 1934 FINISH TESTENG METHODAND APPARATUS Robert Burns, Brooklyn, N. Y.,

assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application October 23,

5 Claims.

This invention relates to testing devices and more particularly to adevice for testing the wearing qualities of surface finishes.

In accordance with the present invention the wearing qualities of asurface finish are determined by rotating a member on which a coating ofthe finish to be tested has been applied in a bath of an abrasivematerial for a predetermined length of time and noting the amount offinish that has been removed from the member.

In the preferred form of this invention the finish to be tested isapplied in any suitable man-- ner to a test piece of the same materialas that on which the surface finish is to be used in practice. This testpiece may be of any size or shape, although for test purposes it ispreferably to employ a thin fiat disk having a circular cross section.The surface finish to be tested is then subjected to the action of anabrasive material for a predetermined length of time. This is preferablyaccomplished by rotating the disk in a hop per containing sand or finelydivided carborundum. The rotation of the disk in the abrasive materialwears off the surface finish which disappears first at the outer edgeand gradually wears in toward the center, thus making it possible tomeasure the wear quantitatively. In order to prevent the abrasivematerial from heating and thus softening the finish under test, a cur-'rent of air is forced through an opening in the bottom of the hopper,thus maintaining the abrasive material in circulation during the test.The dust which is formed due to the constant circulation of the abrasivematerial is removed by any suitable vacuum arrangement.

A clearer understanding of this invention may be had by reference to theaccompanying drawings in which Fig. 1 is a front elevation partly incross section showing the arrangement of parts embodied in theinvention; Fig. 2 a plan view of the test piece and Fig. 3 across-sectional view of the test piece and the apparatus for supportingthe same.

As shown by Fig. 1 a hopper 10 is mounted on a suitable support 11 andis partially filled with abrasive material 12 such as sand or finelydivided carborundum. A test piece 13 on which a layer or a plurality oflayers of the surface 7 finish 14 to be tested has been applied issecured to the flange portion 15 of shaft 16 by screw 17 and is adaptedto be rotated by power supplied by motor 18 through coupling 19. Thetest piece 13 which is preferably made from the same material as that onwhich the particular surface finish is to be used in practice may be ofany size or 1929, Serial No. 401,896

shape but for test purposes it is preferable to use a thin fiat disk asshown. To prevent the escape of abrasive material from the hopper which,if permitted, would cause excessive wear on the bearings in which shaft16 rotates as wellas gradually reduce the amount of abrasive material,that portion of the shaft 16 extending into the hopper is enclosed in ahousing. This housing, as shown by Fig. 3, comprises a rotatable Vshaped bushing 20 which is secured to shaft 16 by set screw 21 and astationary bushing-22, one end of which is fixedly attached to the baseof hopper 10 by screws 23 and the other end of which is'adapted to fitsnugly into the V shaped bushing 20. A collar 24 of soft material suchas felt or rubber serves to prevent any dust from working its way upbetween the contacting faces of the bushings 20 and '22. In order toprevent the abrasive material from heating and .thus softening thefinish under test and also to. keep clean sharp material in contact'withthe finish under test, this abrasive material is kept in con.

stant circulation by means of an injector, which comprises a pipe 26leading from the bottom to the top of the hopper 10 and a similar pipe24, one end'of which is connected to a suitable source of compressed air(not shown). and the other end of which extends into the hopper andterminates in a nozzle-25, the end of this nozzle being slightlyseparated from the opening in the lower portion of pipe 26. When thestop cock 27 is opened, air is forced through nozzle 25 into pipe 26 andthe suction thus formed draws the abrasive material from the bottomportion and redeposits it in the top portion of hopper 10. Any dustformed by the constant circulation of the abrasive material is collectedby bag 27, the dust being forced into the bag by the air which escapesfrom the top portion of pipe 26. The bag 27 is preferably made from aporous material in order to permit the excess air to escape from thehopper. Pipe 28 containing a perforated check valve 31 permits theintroduction of additional abrasive material from time to time to takethe place of the abrasive material which is removed as dust, thusmaintaining the amount of abrasive material substantially constant andalso provides an outlet for the excess air in the hopper. A pipe 29permits a rapid removal of the abrasive material from the hopper 10. a

In operation, the test piece, after being provided with the finish to betested, is buried in the,

interval of time being recorded preferably by a revolution counter 30attached to shaft 16. During this test and all subsequent tests, careshould be taken that the head ofabrasive material on the test piece ismaintained. substantially constant. The rotation of the disk in theabrasive material wears off the finish which disappears first at theouter edge and gradually in towards the center, the actual amount ofwear depending upon the number of rotations that the'test piece makes ina given period of time and the weight of the head of abrasive materialto which the test piece is subjected.

The test piece after being rotated for a predetermined length of time isremoved from the abrasive material and the distance that the surfacefinish has been removed from the outer rim of the test piece in towardsthe center is measured. This measurement, taken in connection with thenumber of rotations that the test piece has made and the weight of thehead of abrasive material to which the test piece has been subjected, isa measure of the wearing qualities of the finish.

This method of test not only gives a measure of the wearing qualities orsurface finishes, but

it also may be employed to indicate the number of coats of finish whichhas been applied to a test piece.

Heretofore it has been difficult if not impossible to determine thenumber of coats of the same finish which have been applied to a givensurface. In accordance with the present invention it is possible to dothis since it has been found that the separate coats do not entirelymerge but remain separate and distinct from each other to such an extentthat a clear line of demarcation becomes visible between the severalcoats when a test piece so coated is rotated in a bath of abrasivematerial in accordance with this invention. The rotation of the testpiece in the abrasive material first wears away the last coat applied,this coat disappearing first at the pcriphery and gradually in towardsthe center of rotation. This leaves a line of demarcation between thelast coat applied and the coat im-' mediately underneath. If therotation of the disk is continued the second last coating applieddisappears in a similar manner and also leaves a line of demarcationbetween it and the coating immediately underneath. By continuing therotation of the disk a line of demarcation is established between eachof the successive coats of finish on the test piece as illustrated forexample by Fig. 2 which shows a 'test piece on which two coats of thesurface finish was applied. After rotating the test piece 13 in the bathof abrasive material 12 for a predetermined length the center ofrotation possess of time, the second coating was worn from the peripheryof the test piece back to line 32 and the first coating applied was wornfrom the periphery back to line 33. These lines were distinct lines ofdemarcation between the test piece and the first and second coats ofsurface finish respectively.

What is claimed is:

1. The method of testing the wearing qualities of a surface finish whichconsists in applying a coating of the finishto be tested to a surface ofa test piece, rotating said test piece about an axis passing throughsaid coated surface in a bath of an abrasive material for apredetermined length of time and measuring the distance from to theinner periphery of the surface from which the finish has been removed.

2. .The method of testing the wearing qualities of a surface finishwhich consists in applying a coating of the finish to be tested on asurface of a test piece of substantially disc shape of the same materialas that on which the surface finish is to be used in practice, rotatingsaid test piece about an axis passing through said coated surface in achamber containing an abrasive material for a predetermined length oftime, maintaining said material in an agitated conditionand measuringthe distance that the finish has been removed from the outer edge intowards the center of rotation of said test piece.

3. The method of determining the number of coats of finish which hasbeen applied to a given test piece of substantially disc shape whichconsists in rotating said test piece about an axis passing through thesurface of said piece having said coats in a bath of an abrasivematerial until the finish has been entirely removed from the outerperiphery of said test piece, and noting the number of lines ofdemarcation on the abraded surface.

4. In a testing device a receptacle containing an abrasive material, amember adapted to be coated with the material to be tested, means forcausing relative movement between said member and said abrasivematerial, and means independent of said first means to agitate theentire mass of said abrasive material.

5. The method of testing the wearing qualities of a surface whichvconsists in applying a coating of the finish to be tested to a surfaceof a test piece of substantially disc shape, rotating said test pieceabout an axis passing through said coated surface in a bath of anabrasive material and measuring on said test piece the radial distanceof exposed surface from which the finish has been removed.-

ROBERT BURNS;

